When objects or fixtures are to be mounted on a wall, the installer searches for a stud into which a screw or nail can be inserted. However, a stud is not always available or in a convenient place. Where an object is to be mounted in hollow wall construction such as plasterboard, sheetrock, fiberboard or any other material employed in hollow wall construction, the common practice is to use a hollow anchor for this purpose. The conventional hollow anchor is formed of metal such as zinc or of plastic such as PVC, which when hammered into a hole pre-drilled into the wall, is then adapted to receive a threaded fastener or mounting screw that goes through the mounting hole in the object and turns into the hollow of the anchor.
The installation of a conventional anchor entails three distinct operations: 1) drilling a hole, 2) hammering the anchor into the hole, and 3) inserting a threaded fastener into the anchor. The first and most critical step is the drilling of a hole in the wall which must be appropriate to that of the anchor. Should an oversize hole be drilled, then in the next step when the anchor is hammered into the hole, the anchor will not wedge firmly therein. As a consequence, it will not be possible to carry out the third step. In the third step, a threaded fastener is inserted into the hollow portion of the anchor. But if the anchor is loose in the wall hole, this will cause the anchor to turn as the fastener is turned, and the fastener will not be able to thread its way into the anchor.
The installation of a convention hollow anchor typically requires several tools including a drill provided with a drill bit having a diameter appropriate to that of the anchor, a hammer to drive the anchor in the hole drilled in the wall, and a screwdriver to turn the threaded fastener into the anchor or to later remove it from the anchor.
Though hollow wall anchors are used on a large scale by installers, the need to drill holes and then hammer the anchors into the holes is a practical drawback, for these operations are time consuming and impose distinct limits on the number of anchors that can be installed in a given period. In addition, if anchors of different sizes must be installed, then the installer must change the drill bit when switching from one anchor size to another, which, consumes time and reduces the productivity of the installer. Furthermore, when a wall anchor is hammered into a wall, the rear surface of the wall board is often destroyed, thereby minimizing the anchor strength of the wall anchor.
One approach to the above is a self-threading anchor with spreadable distal leg portions joined by a frangible drill end portion described in U.S. Pat. No. 5,692,864 to Powell on Dec. 2, 1997. In the '864 Patent, Powell teaches a spade-shaped drill end portion with a frangible web portion which holds the drill end portion together during drilling while allowing the drill end portion to split apart to accommodate the spreading of the leg portions. Other self drilling and self tapping anchors are described in U.S. Pat. No. 5,536,121 to McSherry on Jul. 16, 1996. However, the cutting portions of these anchors create rough cutting surfaces which decrease the strength of the engagement of any external threads. In addition, the rough cutting creates an unsightly appearance after the anchor is installed.
Accordingly, what is needed is an improved anchor bolt which requires a minimum number of tools to install. What is further needed is an anchor bolt which is aesthetically pleasing once installed, and is not unduly disruptive to a mounting surface. What is also needed is an anchor bolt which is securely mounted within a wall for attaching objects thereto.